Fruit supplier Mack, based in Kent, handles 1.3m avocados a week for a number of British retailers, and is testing a new Spanish-developed machine for labelling fruit destined for Marks & Spencer’s shelves.

Cardboard trays of avocados go into a large square contraption and, a few dancing sparks and puffs of smoke later, they emerge the other side with the M&S logo, best before date, country of origin and a till code burned into their skin like an ink-free tattoo.

The British chain hopes to save 10 tonnes of labels and backing paper and five tonnes of adhesive every year by using these lasered labels rather than stickers.

Charlie Curtis, fruit technologist at M&S, adds that laser labelling is also more reliable than stickers which have a tendency to fall off the wrinkly and often slightly damp skins.

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Last year M&S sold 12m avocados and sales this year are up more than 29%.

Adam Shaw, a technical manager at Mack, said demand for avos was rising so fast – “and we don’t see it stopping any time soon” – that the firm has had to add four new specialist ripening rooms for the fruit, taking its total to 16.

Ensuring avocados are ready for mashing on to your breakfast toast is not an easy business. The fruits arrive in the UK graded by size but unripe and hard. They then go into the ripening rooms where they are wafted with warm air for five days.

They are then tested to ensure the avocados are ripe enough for packing: a few sample fruits are stripped of their skin and a gadget called a penetrometer or a fruit texture analyser is used to measure hardness.

A more automated system is on trial which can test lots of fruit by tapping it and listening to the echo. But the system is not yet perfect – Shaw says it needs tweaking so that it can work on fruits with different sizes of stone.

The human touch, however, is still required. Once ripened, the avocados are cooled and hand checked by a group of expert avocado feelers who can tell if a fruit is ripe and ready by just holding and looking at it, but never bruising it.

Fruit from Peru and South Africa is usually in ready supply at this time of year. But supplies have tightened after a late harvest in Mexico, flooding in Peru and drought in California. Strikes by workers in Mexico, which accounts for up to 70% of global avocado production, have added to the problems.

Also 2017 is a “down year” for the crop: avocados naturally alternate between good and poor years for harvest yields.

Shaw said the company has turned to new sources of supply in Colombia as it has become more difficult to meet demand for a fruit which has overtaken berries as its fastest growing product.

“Availability has been tough and the rise in demand from the far east and Asia has also played a part. There is global demand for this fruit,” he said.

Back in the Mack packhouse M&S will soon start more laser trials : avocados, they say, may be just the beginning. The Spanish Laser Food company, which makes the branding machines, has already tested its technology on other kinds of fruit and veg including melons, pumpkins and nectarines.

And M&S has big plans to use the tattoo technology for fun rather than just cost saving reasons - like drawing spooky faces on pumpkins to make it easier for shoppers to cut out Halloween lanterns, and to put smileys on nectarines to make them more appealing to children.